Miniaturization is a central paradigm in the advance of technology. A second paradigm of technologic advance is the continual increase in the complexity of products, which is, in turn, associated with the need for an increase in the number of buttons. These two fundamental paradigms are in opposition, suggesting that as time progresses, the need for smaller (yet useful) input devices will increase as overall product size decreases and the demand for additional functionality continues to rise. While voice technologies will certainly one day offer high-quality, low-cost, near-zero-size input, it is clear that such technology will always be inappropriate for use in such common instances as: a classroom, a meeting, while in mass transit (air or land), a library, etc. Therefore, to provide a continued path for these fundamental technologic advance curves, it is extremely desirable to manufacture low-cost keyboards with both maximal output density and maximal ease of use. Maximal output density means: the most single-touch operations in the smallest space. Maximal ease-of use means primarily two things: 1) Each output must be easily operated as quickly as a user may want without accidentally actuating an adjacent output and 2) in order to be intuitive and natural, the technique for actuating the output should be based on the universally known and accepted “button” paradigms, including use patterns and feel.
The density issue was well-addressed by U.S. Pat. No. 5,612,690 to Levy, but did not address ease-of-use issues. Pertinent prior art includes U.S. Pat. Nos. 4,549,279 and 4,994,992 to Lapeyre. In These patent provide a large number of one-touch accessible operations (4MN−2M−2n+1 in an area of M×N adult human finger widths) by pressing at the adjacent edge, centers, or intersections of full sized keys. U.S. Pat. No. 4,400,593 to Kunz provides the same density using miniaturized tiled keys, however with keys too small to allow edge key operation. U.S. Pat. No. 5,612,690 provides a significant advance to the above mentioned patents by introducing a “volcano” structure to the centers of reduced size keys and substantially increasing the maximal output density to 8MN−4m−4n+1. However, none of these patents discuss the significant and non-obvious barriers to successful implementation of either tiled keyboards, or of keyboards with both individual and combination key outputs.
For example, it is relatively trivial to implement a keyed device that operates only with individual keys, OR only with keys in combination. However, it is very difficult to implement a device that operates quickly and reliably both with individual keys and with keys in combination. To scan for only keys in combination is relatively trivial because reliable output may be determined whenever two opposing keys are registered using well-understood solutions to key switch debounce. However, when the device also outputs individual keys, there is an inherent tension between the desire to provide fast individual key operation and reliable combination key operation. Reason: in order to increase the reliability of combination keys, the time delay to wait for the appearance of all opposing keys in combination must be increased. This increase slows operation of the individual keys. The instant invention addresses this problem to provide fast individual key operation and reliable combination key operation. It is desirable for IACK keyboards to provide fast output response without degradation of the output accuracy.
Some recent advances in the field of IACK keypads are disclosed in my U.S. patent application Ser. No. 09/862,948, filed May 22, 2001, the entire contents of which are incorporated by reference herein as if set forth in their entirety.